Process for hydrogenation of olefins



.l. A. REID PROCESS FOR HYROGENATION OF OLEFINS May 15, 1945.-

Filed Fm.` 13; 1942 Y ber may -beobtained'byth'eadditlcn portions of tetraethyllead. f

f' "Patented May .15, 1945 l UNITED 'STATES )PATENT OFFICE gazeuse A l l .Al-James A. Reid, Bartlesville, Okla., assignor to Phillips Petroleum Company, a corporation of Delaware Application February 13, 1942, Serial No. 430,810 V1 claim. (ci. 26o-683.6)

'This invention relates to aprocess for the nondestructive hydrogenation of olens. It relates morefspecically to a process for the hydrogenation of sulfur-containing folenic stocksfunder l such conditions that deactivation of the catalyst by sulfur4 is minimized;

Itis an objectfof this illfention to provide a.

system for the catalytic hydrogenation of sulfurcontaining olenic stocks, Y

It is a further object of this invention to provide' av means for preventing deactivation of a hydrogenation catalyst by sulfur poisoning.

It is a further object of this inventionto provide a means for increasing the useful life of a catalyst in the hydrogenation of a sulfur-containf ing' oleiinic stock.

It is a furtherl object of this invention to provide a means for simultaneous desulfurizationand hydrogenation of a sulfur-containing oleiinic '20:

stock.

Another object of this inventionv is'to provide f a process whereby unsaturated hydrocarbons are desulfurized in the presence of hydrogenin one stage of a process and in another stage of the process are reacted with hydrogen in the presence of a catalyst.

Other objects will be evident to one skilled in the art from the ifollowing disclosure.

In o rder to increase the vpower output and eillciency ,ofv-internal-combustion engines, it has been necessary to-increase-the pressures' and tem- In spark-ignition engines, the increase in cylinder pressures is limited by the detonation characteristics of the fuels, normally measured in terms of voctane numbers, The detonating characteristicsV A peratures prevailing in the combustionzchaxnber.l

VAlthough minor amounts of 'such branchedchain parafllnic hydrocarbons occur in naturally v occurring hydrocarbon mixtures, the maj or source ofthe highly" branched structure, high octane 6 number parafflnic hydrocarbons is through synthesis Yfrom lower molecular weight olefins. The polymerization of suitable oleflns, auch as isobutylene, normalbutenes, propylene, and in some cases, `ethylene and olens containing live or more carbon atoms per molecule, is well known in the art.. It is frequently desirable to subject these olen polymes to a hydrogenation treatment in order to saturate the olenic bond, so as to improve the storage stability, the increase in octane number on addition of tetraethyl lead, and other qualities.l

hydrocarbons used for solvents, for high octane number fuels, and in various other applications be substantially free from impurities. The exclusion of oxygen and sulfur compoundsespecially is desirable in many cases. For'example, the

"deleterious effects of sulfur on the increase in octane number resulting 'from the addition of tetraethyl lead to motor fuels is well known. -The of Ahydrocarbons depend primarily upon the mo' lecular species, that is, aromatic, oleiinic, ,naph

thenic or paraflinic, upon the extent of carbon chain branching in the individual molecules, and .to lesser extents uponv the molecular weight,"con

centrations in `admixturc with other hydrocarsuch as-tetraethyl lead,-

- 1c has beenfound that the pa'ramn hydrocar- 1 bons; whichare normally,liquid, boil 'belowy about A903 F., and have onevor 'morebranches yin ,their y molecular structure and are very satisfactory as Y' fuelsforhish-,compressionengines. Insomeap'-' ,plicationa similar fuelsloffconslderablyhigher boiling ranges are desirable. Y vare extremely resistant `to gum formation in storvage; they have hig'h octane numbersy in the pure v state, and aconsiderable increase in octane uum-l of smallpro- 55 Suchghydrocarbons 'p removal of minor amounts of such impurities is 'alsoaccomplishe'd through the operation of this process.

`The nonfdestructive hydrogenation of unf-saturated or olefin-containing hydrocarbons is conventionally conducted in the presence ofl a catalytic material which increases lthe rate vat which hydrogen combines with the olenic hydrocarbon and permits a vdecrease in the temprature and pressure necessary-,tc accomplish the desired reaction, thereby facilitating the reaction and minimizing otherchanges accom'- panying the hydrogenation. Two types of catalysts are used in these systems,l the one type, such as: chromium oxide, molybdenum sulfide, tungsten oxide and the like, requiring relatively high temperatures but being ail'ec'ted only in minor vdegree by sulfur compounds, and the `other type, such as reduced nickel, cobalt, copper, platinum and .similar preparations, which in the active state require relatively low; temperatures for 'hydrogenation but which are very susceptible to poisoning and deactivation,- .particularlyvby sul-v zur. compounds.- It is with catalysofthe second type, particularly those containing nick-el, that this invention is concerned.

The hydrogenation catalysts of this second A type contain nickel, copper, cobalt, and similar elemental metals, alone or in combination with other metals, in an active state. The desired activity is in general secured by converting a metal salt or a mixture of the desired metal salts ture with a supporting material for increasing the surface, and in some cases the activity, of the catalytic material. Materials commonly used as catalyst supports include kieselguhr, .dia-

tomaceous earth, pumice, charcoal, porcelainv and the like. @The oxides, hydroxides, or `car- Y bonates may then be reduced in hydrogen or a hydrogen-containing gas to provide the desired catalyt cally active product. One example of such hydrogenationf catalyst is described in U. S. Patent 2,242,627.

. 'CataJysts so prepared vfunction quite satisfactorily in bringing about the additionof hydrogen to oleiins in the preparation of paramn hydrocarbone if catalyst poisons are rigorously'ex- -to oxides, hydroxides, or carbonatos, in a relaf tively pure state, or more frequently in admixnic stocks for'hydrogenation, the sulfur contentof the hydrocarbons and of the hydrogencontaiing'gas is reduced to as low a value asv practica', ,in view oi the known deleteriousl eiect of sulfurandsulfur compounds onfhydrogenacluded from -the system. Conventionally, the olen-containing charge, together with suiilcient diluent or saturated product to prevent Aexcessive temperature increase as a, result of the heat liberated bythe hydrogenation, is passed with tion catalysts 'containing nickel, copper, c obalt, and similarjmetals. .In some commercial opera.-

-tions it has been found that-the sulfur content of olen-contairnng-stocks could not'. economi..`

cally be reduced toa value below-'0.002 toA 0.005'A per cent by weight. AEven higher sulfur values' may result for short' times vas a result of irregularities in operation of lthe desulfurizationv and other processing steps. f

iIn thehydrogenation of such sulfur-'containing ,olen"charge stocks at temperatures inthe an amount of hydrogen in excess of thatcnecessary for complete vhydrogenation of the unsaturated hydrocarbons, through the catalyst mass.

` The pressure in the system may' range from atmospheric to 1000 oreven 2000 pounds Aper square inch gauge,. although pressures in the range of 200 to 800 pounds per square -inch gauge are conventionally used."'I'hejtempera-Vl ture, which is usually maintained at a suiilciently high value to produce the "desired extent e of hydrogenation, is in the range of 250 'to 650 or in some cases as high as '100 F. It is desirable range of from about 250 to about 500. F., using an active nickel-containing catalyst, the zone-ot hydrogenation or of temperature increase in thev catalyst rapidly traverses the catalyst bed in the direction of ow of the charge,- withthe result that the catalyst loses itscapacity tO'bring about the desired extent of hydrogenation of the charge olen ina very short period of operation, usually during the hydrogenation of 10 to 20 volumes of olen'ic chargerl During this time al very small proportion of the nickel,` usually le'ss than 5 .per cent,'hasbee'n 'converted to sulfur compounds.

In contrast, in the h'ydrogenation of similar len' charge containing less than 0.0005 per cent sulto maintain the temperature at as low a value,-

increase in temperature above about 500 F.; and

' especially above about 600 F. Under these conas possible, since hydrocarbon decomposition. and deactivation of the catalyst increase with ditions 0foperation, part of the hydrocarbons are normallyin liquid phase and part in vapor phase, although in the higher temperature and lower pressure ranges all of the charge and product may be in the vapor phase.

The hydrogenation of sulfur-free oleiin stocks appears to occur within a relatively narrow zone in the catalyst bed, as judged by the sharp local .rise in temperature which occurs in an internal zone in the catalyst 'mass during hydrogenation.

Initially, this zone isin the yregion of catalyst which is first contacted by the charge. As the.

catalyst in the initial part of the bed becomesv deactivated or reduced in activity, the' zone of rapid reaction moves progressively down-stream in the catalyst bed,'until iinally the eflluentproduct is inadequately hydrogenated. Increasing the' temperature of the catalyst brings about 'an increase in the extent of hydrogenation, even 'after the catalyst has become partially, de-

activated.

Continued increase of temperatureis not p os- Y sible, however, since catalystV deactivating reactions increase with increase in temperature. Ahighly'active nickel catalyst, Lior example, profur, the same catalyst retains its activity during;

the hydrogenation of more than 1000 volumesoi olefinic charge, 'while operatingdn the same temi' perature' range. i

After the hydrogenation of sulfur-containing oleflns has become incomplete while operating in the temperature range of'from about 250 to about 500 F., the eiilue'nt from the hydrogenation treatyment contains 'a substantial proportion of the sulfur compounds in the charge, lso thatpOiSonresult from the hydrogen `sul'de and morereactive mercaptan sulfur compounds are -rapidly removed byv contact'with nickel. However, other of the sulfur compounds, such as sulfides, disulildes and especially cyclic sulfur compounds; do not react readily with nickel orl other metals 4under those conditions.v 'It'appears to .bethes'e latter types of sulfur compounds which resistihe action of the various desulfurizing treatments.

I have found that in the non-destructive hydrogenatlon o! sinfn-containing oleflnic stocks by,` means o! activecatalysts containing nickel,

copper, cobaltg'and similar elemental` metals,V it

is neces'sary'to maintain the hydrogenation system at a. temperature' aboveabout 500, l. and` usuallyabove about 530 F., depending primarily on the activity of the hydrogenation catalyst, to

duoes appreciable decomposition of olefin poly mers'at temperatures as low as 500 F.;`the decomposition of hydrocarbons, together with deminimize the deactivation of the catalyst resulting irom the poisoning 'effectsof sulfur compounds, andto substantially completely desnl- A ing and deactivation of a second catalystl would. attemptingto complete the hydrogenatipn of the charge. It `has been found that DOunds.

furize the olefinic charge. At those temperatures and above, substantially all the sulfur in oleflnic charge stocks is rapidly converted to metal sulfides or other sulfur derivatives by combination with the elemental metal of the catalyst, so that the remainder ofthe catalyst retains its activity for prolonged periods. As a result of the heat although rapid deactivation resulting from poi- `soning by sulfur is eliminated by operation at temperatures above about 500 F., such operation results in themost active part of the catalyst in the reaction Avessel being subjected to such high operating temperatures that relatively short catalyst lives are obtained in contrast to similar lhydrogenations conducted with sulfur-free stocks at lower temperatures. It is postulated that the yhigh temperature is necessary to bring about the reaction, perhaps after decomposition, of the lessreactive sulfur compounds by means of hydrogenation catalyst of'only moderate catalytic activity. It has further been found that in operations above 500 F., catalysts which have become incapable of bringing about complete hydrogenation of the vunsaturated hydrocarbons in the charge are active for the removal of sulfur -from the charge until more than` half the total nickel,

copper, and other 'sulfur-reactive metals have been converted tOsuldes or other sulfur come During. such operations, ,the substantially complete removal of sulfur from the charge may be achieved even though as little as l0 per cent of the olen charged is being hydrogenated A process has now been developed for securing very long catalyst life in the non-destructive hydrogenation of sulfur-containing olefinic stocks through contacting the olefin-containing hydrovcarbon gas with a hydrogenating catalyst ofv "moderate to low activityatla temperature above labout 500 or preferably above about 530 F. to

secure substantially complete desulfurization and limited hydrogenation of the charge; cooling the desulfurized product from the first step by external means or through the addition of sulfurthe process.

plete, or the sulfurcontent of the effluent increases above a value of 0.0005 to 0.0010 per cent by weight, or untilthe desired extent of hydrogenation cannot be secured in the second stage of Since under favorable conditions one volume of catalyst is capable of catalyzing the hydrogenation of 1000 or more volumes of oleflnic hydrocarbons, the catalyst in the first stage' usually fails to bring about complete desulfurization of the hydrocarbon mixture before the 'ex- -tent of hydrogenation in the second stage falls below the operating limit. It has been observed that in some cases, especially when the desulfurization and hydrogenation catalystA in the first stage contains alumina along with the nickel,

cobalt, copper or other hydrogenating metal or mixture, the lcatalyst at operating temperatures of 600 F. and above will convert the sulfur compounds substantially ,completely to mercaptans and hydrogen sulfide for a 1imited"time after complete desulfurization has failed. This property maybe utilized byvplacing in another reactor between the first and second stages a material capable of removing the hydrogen sulfide and mercaptans from the system, such as suitably lprepared iron and alkaline extracting solutions.

After complete desulfurization is no longer being obtained, or at the time ofv incipient failure, the catalyst in the rst stage of the process may x be removed from thesystem for regeneration,

metal reclamation. and thelike, the catalyst in .thesecond stage may be shifted to be used as free paraflinic diluent; and then contacting the metal hydrogen'ation catalyst at a lower temperature, usually in lthe range of from about 250 to about 500 F. It may be desirable' to 'add additional hydrogen or hydrogen-containing gas prior treatment in the second stage, especiallyif "insufficient hydrogen forcomplete saturation of the olenic compoundsA was added inthe initial steps.- In this process, the catalystin the' desulfurization and partial hydrogenation stagem'ay be prepared-for that purpose, but .preferably it is the catalyst which has previously been usedv as an active'hydrogenation catalyst'in the second stage.

The system is normally4 operated either until a major. portion' of the vs1 1lfurreactive metal in the first stage has been converted tojsulfur comf pounds and the desulfurization becomes incomfhydrogen-hydrocarbon mixture with an active of operation.

recially below 400 F., higher proportions of olei fins may be used, since the latent heat of vaporl ization tends to limit the increase in temperathe catalyst for'the first stage, and a new portion 'of hydrogenation catalyst introduced for use in the second stage.. In case it has been necessary to increase the temperature of the hydrogenation catalyst in the second stage to a value of 600" F., for example,` to secure substantially complete hydrogenation of the olefinic hydrocarbons, it vis not desirable to use it subsequently a's a catalyst for desulfurization and partial hydrogenation in the first stage at a' temperature significantly lowv er than the ,temperature -at which it was previously used.

In controlling the temperatures in this process as indicated, the olefin content of the chargeand the 'extent of hydrogenation must be limited so as to prevent excessive temperature increase,v

since temperature increases as high as 200 F. or more can result from heat liberation on hydrogenation in the substantially adiabatic systems. The addition of paralnic diluent has been found the most satisfactory means of Itemperature control. Thus, in the charge to the second stage or complete hydrogenation, the olefin content of the charge is maintained at values in the range of 20 to '35 per cent, depending upon the temperature At the lower temperatures, es-

ture. l

The hydrogena-tion rateemployed in this proc- `ess depends in `part-upon the characteristics of the charge stock', the limitations of the-various parts of the system, and so forth. Normally from one half to five volumes-of olefinic hydrocarbon of catalyst per hour.

per volume of vcatalyst per hour may be completely saturated in this system. The usual operating rates'are two to four volumes of olefin per volume The operation of this process is schematically illustrated in the drawing. The sulfur-containing olenic charge is introduced through line Il to pump Il, which forces the hydrocarbon stream at the desired pressure, usually betweenj 200 and 800 pounds per, square inch, into line l2. Hy.

drogen or hydrogen-containing gas, usually somewhat in excess of that needed to completely genation, hydrogenated diluent from the second stage may be returned to the first stage through line 62 controlled by valve 63, or hydrocarbon containing a lower proportion of olefinic compounds than the charge to the first stage may be withdrawn from line 2 2 through valve 26 and valve 5I. A portion of the total gas Jmay be passed through line 53 and valve 54 to line 58 for recycle to the second stage. The hydrogencontaining gasmay be treated in hydrogen recoveryl system 52 so as to reject extraneous gases through line 60 controlled by valve 6|, thereby securing a gas containing a greater proportion of hydrogen which' may be removed through bleed-off valve56 or may be recycled through line- 55 and valve 51 to line 58 for transfer by means of compressor 59 into the second-stage hydrogenation system through line 46.

' Various modifications in this'schematic presentation are obvious. In most operations of forced by means of pump 21 through line 28 into line I2.' The total charge in line l2 may then be l passed through I6 into heater i8 wherein itis heated to the` desired temperature, somewhat in I excess of 500. F. For control, part of the charge may flow from line I2.through line l1 to join the hot charge in line 2U. 'I'he charge is transferred through line 1J to the catalyst-containing vessel 2| usuallycontaining a catalyst. of low to moder- Aate hydrogena'tion activity at a temperature above 500 -F.,so controlled as topre'vent rapid deactivation of the catalyst through poisoning by sulfur. There all the sulfur is removed from the ,'charge, and a partial hydrogenation of -the olefins, preferably in excess of 10 per cent,` occurs.

The desulfurized and partially hydrogenatedv charge is conducted by pipe 22 to cooler-23, or throughby-pass line 64 controlled by valve 65', and throughline 25' or, if necessary, through. pump `24 toline 32. lAdditional hydrogen or hy drogen-containing gas may. be introduced intothis stream through line 29 controlled vby'valvel 30. Completely hydrogenated diluent together.

gas may be added to the chargein line 32 through line 46. AThis charge may be passed from line 32 through valve 34 directly to-the second stage hydrogenation .chamber 31', or if a 'higher temperature is needed the charge or a portion of it .between about 250 and about 500 F., is passed into catalyst chamber 31 for complete hydrogenation o the olenic hydrocarbons.A It is de- A -.with recycle hydrogen or 'hydrogen-containing sirable to hold the temperature of the charge to, this system at as low a value as will provide adequate hydrogenat'ion, so as to' hydrocarbondecompositionvand catalyst deterior- V ation which result from contacting active hydrovgenation catalyst with hydrocarbons atfrelatively high temperatures. V

where, after'adequate cooling, the desired product is separated byfractionation or stage separation and withdrawn through line 42 and 4 valve la. The' saturated product which is, de-

sired for recycle to prevent excessive temperatures .in the lhydrogenation stages is through valve 4,4 and transferred by means of pump 45 through line SZ-controlled by valve 63 to the rst'stage orthrough valve 44A and f The saturated hydrocarbon ellluent flows from chamber, 31 through line 38 to separator 4I this type the process is continuous, so that at least three catalyst chambers are desirable to .permit recharging or catalyst regeneration dury heating and cooling required. Modifications and changes may be made in the vprocess stepswith- .out altering the essentials of this process.-

To demonstrate the-valuel of the process in the hydrogenation of sulfurcontaining stocks, the following results are typical and illustrate the advantages of the process of the invention.

Comparative ifcczoerimeni I catalyst was prepared by depositing nickelv and copper nitrateson an Aactivated alumina 'support equivalent to 3.0. pounds of metallic nickel and 1.0 pound of copper per gallon of nished catalyst. preparation was roasted in air at r100 F. to decompose the nitrates, and the resultant nickel and copper oxides were reduced to the metals in hydrogen at 5.50 to 600 F. This catalyst was used tohydrogenate a sulfurfree b lenic polymer, passing through the catalyst mass one volume of 'olen per volume of catalyst per hour, mixed with three volumes of 'previously hydrogenated polymer, together with about 130 per cent of the theoretical amount ofA hydrogen required to saturate the olen in the charge. The hydrogenation was started at 'a temperature of 275 F.; during the hydrogenation of 1145 volumes of olefinic charge to a minimum of 99.5 percent paraflinic hydrocarbons, the

temperature of the charge to the hydrogenati'on system was gradually'increased to a, maximum value of 525- F. From this operation it was evident that the activity of the hydrogenation cat- -alystwas adequate to Vhydrogenate over 1000 volumes of olenic polymer withlnegligibleloss through product decomposition.

Comparative Experiment II the Isame initial .conditions that were' used to I hydrogenate the o1eiinic charge, b ut in this operation the olenic-charge contained 0.006 per cent by weight of sulfur in the form of organic sulfur compounds not removed by washing with alkaline reagents. After ve volumesv of olefin had been treated in the system the-hydrogena' ltion zone, as judged by region of temperature increase in the catalyst bed, had already traversed more thany half the total catalyst volume.

- The temperature of the charge was then increased gradually to 450 F. by the time l0 volumes of olen had been hydrogenated. However,

after 14 volumes of olen had become hydrogenated. the olefin content of the eiliuent product increased rapidly, and even at a charge inlet temperature of 600 F., the product contained about 7 per cent olenic hydrocarbons. 'Ihus this catalyst became deactivated for completel hydrogenation of the sulfur-containing charge during the treatment of only 14 volumes of oleiin. During subsequent operation at 600 F. and above, even though only partial hydrogenation was obtained, the sulfur content of the efiluent was consistently below 0.0010 per cent by weight.

Comparative Experiment III The same experimental conditions, catalyst, and

vof thel heat liberated on hydrogenation. After 110 'volumes of olen vhad been satisfactorily hydrogenated it was necessary to increase ythe inlet temperature gradually to keep the oleiln content of the eiiluent .at a value less than 0.54 per cent.

An inlet ltemperature of 585 F., and .,eiliuent temperature of 670 F. was obtained by the time 195 volumes of olen had been satisfactorily hydrogenated. The catalyst became deactivated quite rapidly thereafter, as a result of the high operating temperature. It is thus evident that the rapid deactivation resulting from poisoning by sulfur compounds was eliminated by main-'- taining-the inlet temperature at a minimum of e 530 F. However, the operation at that elevatedtemperature lcaused a marked reduction in catalyst life, in comparison with the results of Comparative Experiment I.

Example Two hydrogenation systems were assembled in sequence, so arranged 'that desulfurization and partial hydrogenation occurred in the rst stage andj the hydrogenation was completed in the second stage. The catalyst described in Comparative Experiment I was v used in both' catalyst chambers. One volume of an oleilnic chargecontain- Ving .009 per cent of total'sulfur' by'weight, mixed with three 'volumes of paraillnic diluent and- 125 per cent of the theoretical quantity of hydrogen required to hydrogenate the charge, was passed through the rstcatalyst at .an inlet temperatureof 540 F. The charge' rate was that 2 volumes of olen were treated per volume of catalyst per hour. After 90 volumes of the charge had been substantially completely hydrogenad and desulnmmd. the extent of hydrogenation began to decrease, although the d esulrurlzation continued to be satisfactory. The

of the process, the temperature rise through the catalyst increased slowly. After about 340 volumes of olen which had been completely desulfurized and partially hydrogenated in the iirst step of the process had been completely'hydrogenated in this second step, the olen content of the product approached 0.5 per cent. The temperature was then gradually increased until the inlet temperature had reached 560 F., when the efiiuent temperature from the reactor was 650 F. As the olen content of the product increased above 0.5 per cent after a total of 874 volumes of olen had been completely hydrogenated, this operation was stopped. l

The flow to the catalyst in the second stage of the process was changed so that this catalyst became the catalyst for the first stage, to which was then charged the sulfur-containing olen together with parailinic diluent and hydrogencontaining gas, for desulfurization and partial hydrogenation at an initial charge temperature of 550 to 560 F. A catalyst chamber containing freshly prepared or reactivated catalyst was then connected as the second stage or hydrogenation step for repetition of the cycle.

The foregoing example and comparative experiments are recorded to illustrate the advantages of the particular operating conditions of the herein disclosed process. Many other examples, differing in minor details but within the scope of this invention, could be cited. Hence, the inventionshould not be restricted except by the terms or the spirit of the appended claim.

I claim:

A process of substantially completely desulfurizing and nondestructively hydrogenating a sulfur-containing olen hydrocarbon stock consisting essentiallyof olen hydrocarbon which comprises in the ilrst stage contacting one volume of the olenic stock mixed with substantially three volumesof a parailinic diluent and substantially 125% of the amount of hydrogen stoichiometrlclly suillcient to hydrogenate the mixture, withv a sulfur-poisonable elemental metal hydrogenation catalyst consisting of a composite nickel and copper metal hydrogenation catalyst supported on alumina at an initial inle't temperature of substantially 540 F. and a charge rate ofsubstantially two volumes of olen per volume of catalyst per hour, and increasing the inlet temperature to substantially 575 F. as the extent of hydrogenation decreases, then cooling the resulting eflfluent mixture of saturated hydrocarbon, unsaturated hydrocarbon, and hydrogen, to substantially 275 F., contacting said .eiiluent mixture in the second stage with enough additional hydrogen to provide substantially 125% of the amount of inlet temperature wasincreased to, 575' '1". as the 1 extent of hydrogenation decreased, and was held at that value during the substantially complete desulfurization of 874 volumes of sulfur-containing charge, when the hydrogenation in the following step of the process4 became inadequate.

The emuent mixture of saturated hydrocarbon,

.olenncontentoftbechsrincreasedasaxemlt memuoaorwemnmmmm hydrogen stoichiometrically sufiicient to hydrogenate the mixture with an active sulfur-poisonable metal hydrogenation catalyst consisting of a composite nickel and copper hydrogenation catalyst supported on alumina, at substantially 275 F., and as the vol'eiiri content of said eiiiuent mixture increases as a result of deactivation of the catalyst inthe ilrst stage ofthe process increasing Vthe temperature slowly until'the inlettemperature 'of the second stage is 560 F., and then changing the flow of uids and repeating the "method employing the catalyst in the second stage as the catalyst for the first stage and substituting fresh catalyst for the second stage and reg moving the prior first stage catalyst completely fromthe process.

JAMESA. REID. 

